The embodiments described herein relate generally to a detection technique for chemical substances, and, more particularly, to separating components of a sample gas prior to introducing the sample gas into a detector. More specifically, the methods and systems include using a multi-capillary column (MCC) separation device to temporally separate a substance of interest in the sample gas. The systems and methods further include performing an analysis of the separated substance of interest to detect the substance of interest.
Certain contraband substances—such as explosive or narcotics—are difficult to detect in trace amounts. In some cases, environmental interferents reduce detection of these substances of interest. In other cases, a detector mistakenly identifies an environmental interferent as a contraband substance. In some known systems, a membrane inlet is employed at a detector inlet to reduce the problem of environmental interference. However, such membranes not only block out the interferents, but also some portion of the substances of interest, thereby, reducing the detector's overall sensitivity. In other known systems, a single-capillary gas chromatography column is employed to perform gas phase separation of a sample prior to introducing the sample into the detector. However, the long single-capillary column often requires a very long separation time and limits the detector to a low gas flow rate. Such systems are not suitable for applications that require high throughput and large gas volume input. Some such systems provide the single capillary column in a coiled arrangement within a large, bulky oven to heat the column to higher temperatures for sample separation, but such ovens are not practical for use in applications where space may be limited.